The present invention relates to a color copying apparatus which forms a color image on a transfer material which reciprocates with respect to a photoconductor on which a color toner image to be transferred is formed.
The above mentioned kind of color copying apparatus comprises an endless conveyor belt for conveying the transfer material which conveyor is driven to move forward and backward repeatedly. An image of one color is transferred on a transfer material, i.e. on a copy paper during a forward movement of the conveyor belt. Then the belt is moved backward and again moves forward so that the image of a second color is transferred during this subsequent forward movement. With such an arrangement of the color copying apparatus, the conveyor belt comes in contact with the photoconductor in the forward movement of the conveyor to transfer the color toner image from the photoconductor to the copy paper, whereas the conveyor belt must be shifted away from the photoconductor surface in the backward movement of the conveyor belt in order to avoid damaging the unfixed toner image formed on the copy paper being conveyed by the belt by contacting with and rubbed by the photoconductor surface. In this case, the required length of the gap between the photoconductor surface and the conveyor belt is very small, since even a very small length of the gap is enough for avoiding the contact therebetween.
On the other hand, if the gap is small, it is inconvenient at the time of maintenance of the apparatus such as changing the photoconductor or repairing jamming of the paper. Therefore, a large gap between the photoconductor and the conveyor belt is required from the standpoint of the maintenance operation.
There has not been developed so far a color copying apparatus which comprises a means for shifting the conveyor belt which means satisfies the above mentioned two contradictory requirements.